The field of conventional mixing devices can be roughly divided into two main areas: mechanical mixers and static mixers. Mechanical mixers rely on some type of moving part or parts to impart energy into the fluid components being mixed. Static mixers generally have no prominent moving parts, and instead rely on the pressure drop of one or more of the fluids to serve as the source of mixing energy. Conventional mixer tees are a type of static mixer.
Multi-tee mixers having a tee-pipe junction and a straight pipe section with nozzles and blind flanges are usefully employed for rapidly initiated reactions The junction contains a mixing chamber having separate inlets for at least two substances and an outlet. Typically, the inlet for one of the substances is provided within the axis of the mixing chamber and the inlet for the other substance or substances is constructed in the form of a plurality of nozzles or jets arranged rotationally symmetrical to the axis along the circumference of the mixing chamber.
The quality of the products prepared in an apparatus of this type depends on the quality and rate of mixing of the fluid substances. The quality and rate of mixing can be affected by fouling, caking, or plugging of the jets of the inlet of the mixer tee and results in decreased performance. Over the course of time, caking and subsequent clogging disturbs the injection and the distribution of flow through the jets. The risk of clogging increases where the substance that passes through the nozzles is dissolved or suspended in a solvent or in a suspending medium and the solvent or suspending medium is separated from the product and reused. Caking may also occur on the mixer-side surfaces of the jet as a result of secondary reactions. Where caking and/or clogging occur, a continuous process has to be interrupted and the tee mixers taken apart and cleaned. This causes undesirable idle periods. Where hazardous substances are used, industrial hygiene regulations necessitate expensive measures during the disassembly of the tee mixers, such as the thorough flushing of the system before disassembly, exhaustion of the atmosphere, protective clothing, and breathing apparatuses for the worker. Each of these measures adds to the overall cost, reduces throughput, and reduces the efficiency of the process.
Some chemical reactions require rapid mixing with minimal back mixing. Back mixing can allow a product of an initial reaction to react with another component in the reaction stream to generate an undesired product. Back mixing can contribute to by-product formation and mixer fouling. Consequently, mixer designs that do not account for back mixing issues can result in lower overall yield of the desired product or can generate a product that clogs or fouls the reactor system leading to down time and/or increased maintenance costs.
Therefore, there is a need for a mixing device that provides rapid mixing of reactants, yet provides a reaction system that does not suffer from unacceptable fouling, particularly of the jets of the mixer-tee.